This invention relates to permanent magnet DC brushless motors and more particularly, to such motors combined with a bi-directional control system.
Permanent magnet DC brushless motors generally include stationary windings, a rotating permanent magnet field and rotor position sensors connected to control winding energization. The energy supplied to the stator windings is usually controlled by solid state drive switches which are selectively rendered conductive by the position sensors in accordance with the rotor position. The drive switches are generally controlled via logic circuits responsive to the position sensor signals as well as other control signals.
The brushless DC motor eliminates the DC commutator as well as other problems commonly associated with the commutator. On the other hand, even though the brushless motor systems can be more reliable and more effective, particularly in high performance servo applications, these results are usually achieved by incorporating relatively complex and expensive switching logic and control circuitry.
An object of this invention is to provide a simpler and less expensive brushless motor control system.
Another objective is to provide a brushless motor wherein the switching circuits and control logic can conveniently be located within the motor housing.
Still another object is to provide a brushless DC motor system wherein bi-directional control and duty cycle modulation control can be achieved at no additional expense.